1. Field of the Invention
The present invention generally relates to a liquid-crystal display unit, and more particularly, to a liquid-crystal display unit displaying an image on a liquid-crystal panel.
2. Description of the Related Art
FIG. 1 is an illustration showing a structure of a conventional liquid-crystal display unit. As shown in FIG. 1, a liquid-crystal display unit 11 comprises a pixel electrode board 1, thin-film transistors (TFTs) 2, signal lines 3, scanning lines 4, a common electrode board 5, a common electrode 6, a liquid-crystal layer 7, a signal-line drive circuit 9, a scanning-line drive circuit 10, and pixel electrodes 23. The TFTs 2, the signal lines 3, the scanning lines 4, the pixel electrodes 23, the common electrode 6, the liquid-crystal layer 7 provided between the pixel electrodes 23 and the common electrode 6, compose a liquid-crystal panel.
FIG. 2 is a plan view showing a layout of a pixel matrix formed on the pixel electrode board 1 shown in FIG. 1. As shown in FIG. 1 and FIG. 2, the TFTs 2, the pixel electrodes 23 each connected to the TFT 2, the signal lines 3, the scanning lines 4, the signal-line drive circuit 9 driving the signal lines 3, and the scanning-line drive circuit 10 driving the scanning lines 4 are formed on the pixel electrode board 1. The common electrode 6 is formed on the common electrode board 5.
Also, as shown in FIG. 2, the pixel electrodes 23 are formed in the form of a matrix on the pixel electrode board 1. The signal line 3 supplies an image signal to the pixel electrode 23. The scanning line 4 transmits a control signal to a gate of the TFT 2, the control signal turning on/off the TFT 2 which is connected to the pixel electrode 23 so as to regulate writing of data to each pixel.
It is noted that a unit like the liquid-crystal display unit 11 that drives the signal lines 3 and the scanning lines 4 so as to display an image by means of liquid crystal via the pixel electrodes 23 formed in the form of a matrix is referred to as an “active matrix liquid-crystal display unit”.
On the other hand, there is also another conventional liquid-crystal display unit, as a second type of the active matrix liquid-crystal display unit, comprising a printed circuit board formed of glass epoxy resin, the printed circuit board having the signal-line drive circuit 9 and the scanning-line drive circuit 10, and a pixel electrode board formed of glass, the pixel electrode board having the pixel electrodes 23, the signal lines 3 and the scanning lines 4, wherein the printed circuit board and the pixel electrode board are connected to each other by a flexible cable.
However, the conventional liquid-crystal display unit 11 as the active matrix liquid-crystal display unit shown in FIG. 1, especially a liquid-crystal display unit of, so to speak, an all-peripheral-circuits-in-one type having an operating semiconductor layer of a TFT formed of polycrystalline silicon (polysilicon: p-Si), is provided with more than multimillion pixel electrodes 23 and a multitude of circuits such as the signal-line drive circuit 9 and the scanning-line drive circuit 10 both consisting of numerous circuit components, all of which electrodes and circuits are formed on the pixel electrode board 1; therefore, such a conventional liquid-crystal display unit incurs a high possibility that at least one of those electrodes and circuits thereof be manufactured inferiorly. Then, when even one of those elements is actually manufactured inferiorly, the pixel electrode board 1 falls out of use even though all other elements function normally; thus, the conventional liquid-crystal display units suffers a problematically poor yield rate.
On the other hand, the above-mentioned second type of the active matrix liquid-crystal display unit is difficult to design because of the structure thereof in which the printed circuit board and the pixel electrode board having different coefficients of thermal expansion are connected to each other by a flexible cable. Furthermore, the above-mentioned second type of the active matrix liquid-crystal display unit provides little reliability in operation since conditions in the connection part vary depending on the operating temperatures.